A fiber reinforced polymer (FRP) is a composite material including a polymer matrix reinforced with fibers such as glass, carbon, or plastic to improve the strength, rigidity, and impact resistance of the polymer. The properties of an FRP depend on the fiber length, fiber distribution, and fiber orientation within the polymer matrix. In order to optimize one or more properties of the FRP, the length distribution of fibers present in various samples of the FRP can be measured.
To measure the distribution of fibers of different lengths in a FRP sample, the fibers can be separated from the polymer matrix using heat. The fibers can then be suspended in a liquid and sorted according to length using a stack of sieves having progressively smaller screens. The weight of fibers present in each screen after the sorting process can be determined in order to calculate the overall fiber length distribution for a given sample of the FRP. However, the fibers have a tendency to attract each other, with smaller fibers adhering to longer fibers within the layers of the sieve stack, skewing the fiber length distribution results.